"Selenium is found in nuts and seeds and it's also found in meat, poultry and eggs and fish," Bannan said.

She added that tryptophan is also present in nuts, seeds and protein foods while folic acid is present in fortified grains and produce. And while these foods are common, those who don't eat them may have problems.

"There was a 2012 study in Public Health & Nutrition that found that people who ate the most junk food, which was commercially baked goods and fast food, had the highest incidents of depression," Bannan said.

On the other hand, choosing brain-boosting food makes a difference long term.

"These are things that are helping the brain sustain itself help build the foundation for neural health," Noonan said.

Such foods can be found even in a pizza place. Healthy doesn't have to be bland or boring.